As a thought, I believe the price dropped about a dollar at the open. This would pull in a lot of daytraders, which would make up a lot of the volume. This year at ASCO a company released news of a launch of a liquid biopsy, pre market. It traded high volume in the pre-market. The stock has lesss than 14 milllion shares outstanding, but the volume that day was a staggering 27 million shares. A lot of shenanigans that day and for weeks after as they had a lot of stuck traders to clear out.